Composition storage battery separator and method of making the same



Patented Aug. 10, 1943 COMPOSITION STORAGE BATTERY SEPA- IStATOR ANDMETHOD OF MAKING THE Bruno H. Schubert, Weehawken, N. J assignor toNational Lead Company, New York, N. Y., a corporation of New Jersey NoDrawing. Application October '2, 1941, Serial No. 413,300

9 Claims.

The present application is a continuation-inpart of my copendingapplication, Serial No. 267,- 923, filed April 14, 1939, which issued asU. S. Patent No. 2,290,496 on July 21, 1942.

The invention herein described and claimed relates to storage batteriesof the lead-acid type, particularly having reference to the use in suchtypes of storage batteries of an improved separator manufacturedaccording to the method herein described. The objects of the inventioninclude, among others, the manufacture of an improved type of storagebattery separator as well as the use of such improved separator instorage batteries of the lead-acid type, thereby to impart to the storagbattery an improved discharge capacity and a longer life. The novelseparators of the present invention are characterized in that theycontain as an integral part thereof an added active organic ligneouscompound.

Bythe term organic ligneous compound? as the present invention.

remain, after treatment, in the structure of the wood. Inasmuch as theseorganic ligneous compounds are present in all forms of vegetablesubstances, the particular type of vegetable substance from which theactive organic ligneous compound is derived is of no consequence inthepractice of Wood is a very convenient source for obtaining theseactive organic ligneous compounds, as are also straw, hemp. jute,

.corncobs, bagasse, humus, peat moss, etc. The

available source of organic ligneous compounds. P

useful in the practice of the invention. On the whole, the sources fromwhich active organic ligneous materials may be derived are well understood by those skilled in the art.

used in the description of the present invention are meant all of thoseorganic materials of extremely complex chemical nature which are presentin all forms of vegetable matter other than the cellulose, fats, waxes,resins, wood acids and salts of wood acids, and said turn also embracesthe derivatives of such complex chemical materials, addition anddecomposition products thereof For a better understanding of suchcomplex organic ligneous compounds, reference is made to the book, Humusby Selman A. Waksman (The Williams andWilkins Company, Baltimore, Md.),second edition 1938, page 99.

It is not possible to state what is the true chemical nature of ligninor of organic ligneous ma-.

terials; chemical science has not yet determined the structure thereof.It is known, however, that when substances of vegetable origin aresuitably treated with acidic materials such as calcium acid sulflte,alkalies or some organic solvents, such as dioxane, there ar obtainedsolutions containing among other things some of the ligneousmaterials'originally present in the vegetable substances. Separated fromthe naturally occurring fats, waxes, resins, wood acids and salts ofwood acids also present in the vegetabl substance the organic ligneousmaterials, I have found, possess properties which are conducive tobetter battery performance when added to separators, and I havedesignated such ligneous compounds in the description of the presentinvention and in the appended claims as active organic ligneousmaterials. Such a designation will serve to distinguish over thoseunextracted inactive ligneous compounds which are originally found andwhich It has been known, prior to our invention, that if lignin andligneous materials be incorporated into the negative plate of alead-acid type storage battery, certain desirable efiects, in the natureof greater discharge capacity, were imparted to the storage battery. Inthe manufacture of storage battery separators the most commonly employedmaterial used up to now has been wood. A separator fashioned from woodistreated, for example, with caustic alkali solutions, to remove from art,was therefore substantially free of any fats,

waxes, resins, wood acids, salts of wood acids, all of which areregarded as detrimental to storage batteries of th lead-acid type.

As noted above, in the treatment of wood separators with caustic sodasolution, there is removed in addition to the fats, waxes, resins, woodacids, and the like some of the ligneous'materialwhich is uncombined orloosely combined in the wood structure, possibly 2-3% ,of the totalligneous substance content. A large proportion of this calledhemicellulose ligneous organic combination apparently is inefiective inproducing improved separators, and I have found it to be necessary toadd the so-called active ligneous material to the treated woodseparators in order to impart to a storage battery improved life and lowtemperature capacity.

Therefore, it should beunderstood that untreated wood separators do notexhibit the improved properties of my treated separators, and

that the ligneous material originally available in the wood is not inthe proper active form to produce the desired improvements. Furthermore,it

- has been found desirable, in the practice of my invention, to effect auniform distribution of the active ligneous compounds over the surfacesof the separators with sumcient penetratlonto anchor the products whenthe organic is set by the acid-fixing treatment.

While pre-fabricated separators have been mentioned above in order thata clearer understandingof the background of the present-invention may behad, it is to be understood'that the present invention is concerned withcomposition separators and methods for preparing the same. The treatmentof prefabricated separators has been more fully described and claimed inmy copending application, Serial No. 267,923, now U. S. Patent No.2,290,496, dated July 21, 1942, of which as hereinabove mentioned, thepresent application is a continuation-in-part.

According to the present invention, I have found that if an activeorganic ligneous compound, either in the form of a dry powder or as aliquid is incorporated as one of the constituents from which a separatoris compounded, the resulting so-called composition separator has theunusual property of imparting greater discharge capacity and a longerlife to the storage battery. In the manufacture of compositionseparators suitable for use as insulating media in storage batteries,any of the well known ingredients suitable for the purpose may beemployed, depending upon the particular manufacturers choice.

Fundamentally, the ingredients will comprise a rubber vehicle, either ofthe latex type, the

gum type or a combination of both. In addition, the ingredientswillinclude suitable vulcanizing agents and accelerators in addition tofillers or porosity agents such as wood pulp, bentonite and the1ike,,and in the case of my improved separators, an active organicligneous compound in amounts between about 0.01 per cent and about 5.0per cent of the weight of the separators and preferably between about0.25 per cent and about 2.0 per cent. in order to illustrate suitableingredients that may be used in manufacturing composition separators, aspecific example is given below. It is to be understood, however, thatthis example is given for illustrative purposes only and that myinvention is not to be limited to the specific ingredients thereinrecited. The main objective of the present invention resides in theaddition of an active organic'ligneous compound to the constituents ofthe separator, thereby to improve battery performance, especially. atlow temperatures.

Example Composition separators were prepared by thoroughly mixing thebelow-listed ingredients in pro- Water The active organic ligneouscompound, which is insoluble in water and sulfuric acid, may be addedeither as a dry powder or as a liquid and is thoroughly mixed with theother constituents in order to obtain good distribution throughout theseparator mass.

The separator mass is then formed or molded by a pressure operation,such as by passing it between suitable rolls, and then vulcanized withheat, preferably in a moist atmosphere. 'The formed product is then cutup into separators of the desired shape andsize. The finished separatorshould contain sufiicient voids or porosity so as to permit free passageof the electrolyte through the'separator .when it is assembled into thebattery. The percentage of the voids will vary depending upon theconstituents used in making the composition separators. However, it isdesirable that the voids constitute at least 50% of the separatorvolume.

Composition separators obtained from the foregoing example were made upinto standard type lead-acid storage batteries; These batteries werethen subjected to a standard discharge test in comparison with otherbatteries made up with composition separators fabricated from identicalingredients but not containing the active organic ligneous compounds.The technique on the tests was as follows:

The batteries undergoing automatic life tests were subjected to adischarge of 300 amperes at 0 F. and a cut-out of one volt per cell or 3volts for the entire battery. When the battery was completelydischarged, it was fully charged and again discharged under the sametest conditions, the discharge and charge being considered as one cycle.As the cycles of discharge and charge follow one upon the other, theduration of time of the discharge portion of the cycle becomes shorter,so that after any given number of cycles that-battery whose dischargeoutput is greater than another battery is said to have abetter lowtemperature capacity characteristic.

Under these conditions the results obtained in testing the batteriesprepared with the separators obtained according to the aforesaid exampleand those obtained with batteries containing untreated separators wereas follows:

Duration of discharge portion of cycle- No.of seconds cycles TreatedUntreated 4 The improved result of our invention is most pronounced atthe period when it is most needed, namely, after numerous cycles ofdischarge and charge and particularly effective under the most severeoperating conditions, viz., cold weather. Furthermore, the improvedresult is not dependent upon nor associated with the presence of anorganic expander in the negative plate. The improvement of the presentinvention is obtained regardless of whether the negative plate of thebattery contains an organic expander or not. Where expanders are used inthe negative plates in conjunction with the present invention, it-appears that the effect of the improved separator makes itself feltmost prominently about the time-the eflect of the organic expanders ofthe negative plate begins to be dissipated.

When the novel separators of the present in- 'the following as new anduseful:

vention are incorporated into storage batteries of the lead acid type,batteries are obtained which possess greater discharge output capacityand longer life, especially at low temperatures, which, over a 300350cycle life test period, is seldom less than 40 per cent greater than asimilar battery containing the separators of the prior art and in manycases is as much as 100 or more per cent greater,

By virtue of the improved results above set forth, it is easily possibleto distinguish between my improved composition separators and those ofthe prior art. However, a simpler and quicker test for identifying myimproved separators from those of the prior art is to cut up therespective separators and treat the pieces with a 2-3% caustic sodasolution. The extracted matter dissolved from my improved compositionseparator will, because of the presence of the active organic ligneouscompound, impart to the caustic soda solution a considerably intensifiedcolor which will be lacking in the case of ordinary separators.

Having thus described my invention, I claim 1. Method of manufacturingan improved composition storage battery separator composed.

essentially of porous rubber which comprises in timately mixing a smallamount of an active organic ligneous compound with theprimaryconstituents from which the separator is fabricated andthereafter fabricating the separator.

2. Method of manufacturing an improved composition storage batteryseparator composed essentially of porous rubber which comprisesintimately and uniformly mixing a small amount.

composed essentially of porous rubber having' as porous rubber whichcomprises intimately and uniformly mixing with the primary constituentsfrom which the separator is fabricated an amount of an active organicligneous compound between about 0.25 and about 2.0 per cent by weightand thereafter fabricating the separator.

6. A composition storage battery separator composed essentially ofporous rubber having incorporated therein a small amount of an activeorganic ligneous compound.

'7. A composition storage battery separator composed essentially ofporous rubber containing uniformly distributed throughout its pores andupon its surfaces a small-amount of an active organic ligneous compound.

8. A composition torage battery separator composed essentially of porousrubber having as one of the ingredients thereof an active organicligneous compound in an amount between about 0.01 per cent and about 5.0per cent based on the weight of the separator.

9. A composition storage battery separator one of the ingredientsthereof an active organic ligneous compound in an amount between about0.25 per cent and about 2.0 per cent based on the weight of theseparator. I

= BRUNO H. SCHUBERT.

